1. Field of the Invention
The present invention relates to a cable cutting apparatus to be used in cable handling works for cutting cables such as signal transmission cables and power supply cables.
2. Description of the Background Art
The cables such as the signal transmission cables and the power supply cables are important means for conveying information or energy to distant places. Because such cables are to be connected between distant places, such cables are usually laid in a form of a bundle of a plurality of cables through telephone tunnels, telegraph poles, raceways, racks, etc. In such a bundle of cables, an individual cable is distinguished from the other cables of the bundle by the feature such as its thickness, a color of its covering material, a material of its covering material, etc.
However, the bundle of cables usually contains several tens to several hundreds of cables together, so that it is almost inevitable for any bundle to contain more than one cables of the same kind. Consequently, in order to distinguish each cable clearly, it has been necessary for each cable to be attached with a number of tags indicating a type or a use of each cable, at regular intervals along each cable.
Now, in recent years, as our society becomes increasingly information-oriented, a number of cables to be laid has been increasing considerably, such that a huge number of old and new cables are now laid within a rather narrow cable laying space available. In addition, in conjunction with the rapid progress of various data processing devices, a demand for the cable handling works such as cable location changing works, cable type changing works, and cable removing works is also increasing considerably.
For example, in order to remove or change a location of an old data processing device, there is a need to carry out an old cable handling work at a cable laying space at which the old cable is located. In such an old cable handling work, as the cable laying space becomes narrower, the proper checking of the tags attached to the cables becomes increasingly difficult, and as a result, there is an increasing amount of danger to cut off the cable in use by mistake.
In general, the cable handling work is carried out in the procedure of checking a location to carry out the cable handling work on a cable layout design specification in advance, and then carrying out the following four operations at the actual work cite: (1) cutting of the old cable; (2) pulling out of the old cable; (3) reeling out of the new cable; and (4) laying of the new cable; where the operations (3) and (4) are unnecessary in a case of the cable removing work. In any case, the operation (1) of the cutting of the old cable is the step that requires the most caution in the cable handling work, because in a case of cutting off the cable in use by mistake, an operation to re-connect the erroneously cut off cable together requires an operation time which is several tens to several hundreds times that of the cable cutting operation.
In order to avoid such a trouble related to an erroneous cutting of a cable in use, a cutting target cable recognition apparatus has been employed conventionally, as shown in FIGS. 1A and 1B.
Namely, in FIG., 1A, an old cable 103 is connected between two old data processing devices 101 and 102, and laid along with other cables in use 104, 105, and 106 of the type similar to that of the old cable 103 which are connected between other data processing devices (not shown).
Usually, the old data processing devices 101 and 102 themselves are located outside of a view field of a cable handling worker working in a cable laying space, so that the cable handling worker is required to pick out the old cable 103 from a number of similar cables.
To this end, conventionally, the old cable 103 is disconnected from the old data processing devices 101 and 102, and a standard identification signal of 270 Hz from a signal injector 108 attached at one end of the disconnected old cable 103. Then, the identification signal transmitted through the old cable 103 is detected by a weak signal detector 110 placed in a vicinity of the old cable 103 and a detection by the weak signal detector 110 is indicated to the cable handling worker by a signal indicator 111 connected with the weak signal detector 110, such that the cable handling worker can identify the old cable 103 to be cut off, non-destructively.
More specifically, as shown in FIG. 1B, the signal injector 108 is attached to one end 107 of the disconnected old cable 103, while another end 109 of the disconnected old cable 103 is closed by Joining the signal lines so as to loop back the signal transmitted through the old cable 103. Then, the identification signal of 270 Hz is injected by the signal injector 108 and transmitted through the old cable 103. Then, the identification signal transmitted through the old cable 103 is detected by the weak signal detector 110 placed by the cable handling worker in a vicinity of the old cable 103 at a desired location along the old cable 103 and a detection by the weak signal detector 110 is indicated to the cable handling worker by the signal indicator 111, such that the cable handling worker can identify the old cable 103 to be cut off at the cable laying space, non-destructively.
Here, the old cable 103 is usually a part of a bundle of a number of cables, so that in order to remove this old cable 103 alone, it is necessary to cut this old cable 103 into many pieces, by carrying out the cutting operation at number of positions along the old cable 103. On the other hand, when the old cable 103 is cut at one position, the closed loop of the old cable 103 is opened, such that the transmission of the identification signal becomes difficult.
For this reason, conventionally, markings are marked to the cutting positions on the old cable 103 determined in the manner described above in advance, before the actual cutting operations are carried out.
However, this procedure is rather involved one, which is both tedious as well as time consuming, so that this conventional cutting cable discrimination apparatus using the signal injector 108, the weak signal detector 110, and the signal indicator 111 is hardly used in practice.
In addition, in this conventional cutting cable discrimination apparatus, the apparatus itself is too expensive to equip every one of numerous cable handling work cites with this cutting cable discrimination apparatus permanently.
Moreover, because the detection sensitivity of the weak identification signal is low, it is difficult to detect the weak leakage of the identification signal from a cable laid near a center of the bundle of a plurality of cables.
It is to be noted here that, in principle, it is also possible to detect the identification signal transmitted through the old cable 103 even without a closed loop at another end 109, provided that the injected identification signal is sufficiently powerful.
However, in practice, this procedure tends to result in a failure to detect the very weak leakage of the identification signal by the weak signal detector 110.